A Two-Degree of Freedom Variable Stiffness Actuator Based on The MACCEPA Concept

The current state of the art of variable stiffness actuators consists mostly of different concepts for single degree of freedom joints. However, in bio-inspired robotic applications multiple degree of freedom variable stiffness actuators are often desired. Currently this is usually achieved by cascading single degree of freedom actuators. The innovation presented in this work is a two degree of freedom variable stiffness actuator using the MACCEPA concept. The presented actuator is not a cascade of two single degree of freedom actuators, but centralizes the two degrees of freedom in one single joint. Equilibrium position and stiffness of the actuator are, furthermore, independently controllable in both degrees of freedom. The design and experimental validation of the actuator are discussed in this work. The independence of adjusting equilibrium position and stiffness of the actuator are experimentally validated. The results show that the measured characteristics of the actuator sufficiently match the theoretically calculated ones. Future work includes implementing the presented two degree of freedom actuator in an application like a bipedal robot or a robotic arm.